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| United States Patent |
6,138,690
|
|
Nakatani
|
October 31, 2000
|
Method and an apparatus for the wet treatment of a semiconductor wafer
Abstract
A method for the wet treatment of a semiconductor wafer comprised of
subjecting a semiconductor wafer to chemicals treatment, rinsing with pure
water and drying by direct transfer of the wafer to an atmosphere of a
vapor containing an alcohol, wherein the semiconductor wafer is treated
with a solution containing a semiconductive particle-removing agent during
the interval between the steps of the chemicals treatment and the drying.
The semiconductive particle-removing agent is one which is able to control
the zeta potential of the particles to prevent the deposition of the
particles. Alternatively, semiconductive colloid coagulants may be used
which inhibit the formation of the particles by coagulation of
semiconductive colloids. Thus, deposition of particles on a wet-treated
semiconductor wafer is prevented.
| Inventors:
|
Nakatani; Norikazu (Tokyo, JP)
|
| Assignee:
|
Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
950836 |
| Filed:
|
October 15, 1997 |
Foreign Application Priority Data
| Current U.S. Class: |
134/1.3; 134/2; 216/90; 257/E21.251 |
| Intern'l Class: |
B08B 006/00; C03C 023/00 |
| Field of Search: |
134/1.3,2
216/90
|
References Cited
U.S. Patent Documents
| 5002618 | Mar., 1991 | Kanai et al. | 136/258.
|
| 5148823 | Sep., 1992 | Bran | 134/184.
|
| 5520744 | May., 1996 | Fujikawa et al. | 134/11.
|
| 5733434 | Mar., 1998 | Harada et al. | 205/746.
|
| Foreign Patent Documents |
| 731498 | Sep., 1996 | EP.
| |
| 4209865 | Sep., 1993 | DE.
| |
| 2-309637 | Dec., 1990 | JP.
| |
| 4-6830 | Jan., 1992 | JP.
| |
| 5-96220 | Apr., 1993 | JP.
| |
| 5-315311 | Nov., 1993 | JP.
| |
| 6-097141 | Apr., 1994 | JP.
| |
| 6-326073 | Nov., 1994 | JP.
| |
| 7-230975 | Aug., 1995 | JP.
| |
Primary Examiner: Utech; Benjamin L.
Assistant Examiner: Goudreau; George
Attorney, Agent or Firm: McDermott, Will & Emery
Claims
What is claimed is:
1. A method for wet treatment of a semiconductor wafer which comprises the
steps of:
treating a semiconductor wafer in a treating vessel with a chemicals
solution;
rinsing said semiconductor wafer with pure water; and drying said
semiconductor wafer by direct transfer to an atmosphere of a vapor
containing an alcohol;
wherein said semiconductor wafer is treated, either with a solution
containing a semiconductive particle-removing agent, or with a
semiconductive particle-removing agent during the course between said
treatment with the chemicals solution and said drying,
wherein said semiconductive particle-removing agent is an agent for
preventing adhesion of particles by controlling a zeta potential of the
particles,
wherein said semiconductive particle-removing agent is added to pure water
for rinsing in at least a part of said rinsing process.
2. A method for the wet treatment of a semiconductor wafer according to
claim 1, wherein said semiconductive particle-removing agent is added to
the pure water left in said treating vessel of said semiconductor wafer,
after the pure water has been passed through said treating vessel for
rinsing said semiconductor water.
3. A method for the wet treatment of a semiconductor wafer according to
claim 1, wherein said semiconductive particle-removing agent is added to
the pure water being passed in a part of said rinsing process, wherein the
pure water is being passed through said treating vessel for rinsing said
semiconductor wafer.
4. A method for the wet treatment of a semiconductor wafer according to
claim 3, wherein said semiconductive particle-removing agent is added to
the pure water being passed through said treating vessel, of said
semiconductor wafer, for rinsing said semiconductor wafer, and thereafter
pure water alone is further passed through said treating vessel, of said
semiconductor wafer, for rinsing said semiconductor wafer.
5. A method for the wet treatment of a semiconductor wafer according to
claim 1, wherein said semiconductive particle-removing agent is added to
the pure water being passed during an entire rinsing process, of passing
the pure water through said treating vessel.
6. A method for wet treatment of a semiconductor wafer which comprises the
steps of:
treating a semiconductor wafer in a treating vessel with a chemicals
solution;
rinsing said semiconductor wafer with pure water; and
drying said semiconductor wafer by direct transfer to an atmosphere of a
vapor containing an alcohol;
wherein said semiconductor wafer is treated, either with a solution
containing a semiconductive particle-removing agent, or with a
semiconductive particle-removing agent, subsequent to said rinsing of said
semiconductor wafer.
7. A method for the wet treatment of a semiconductor wafer according to
claim 6, wherein said semiconductive particle removing agent comprises
aluminum sulfate or polyaluminum chloride.
Description
FIELD OF THE INVENTION
This invention relates to a method for the wet treatment of semiconductor
wafers in a process of manufacturing semiconductors and also to a wet
treating apparatus for conducting the method.
BACKGROUND ART
In the wet treating step of the semiconductor-manufacturing process, it is
essential to dry the semiconductor wafer without causing any water marks
to be formed on the wafer. In prior art drying techniques, there are known
"dry spinning" methods wherein a wafer is rotated to dry by spinning out,
and "IPA vapor drying" methods wherein a wafer is transferred to an
atmosphere of an IPA vapor and dried. These techniques commonly have the
problem that water marks are formed during the course of transfer from
final rinsing to drying. Attention has now been made, as a substitute
therefor, to techniques of the "Marangoni drying" method, wherein a wafer
is dried by transferring from water to an IPA vapor atmosphere, and the
"drying by direct substitution with IPA" method, wherein a layer of IPA is
formed on the surface of the water to directly substitute the water with
IPA.
In the conventional wet treatment methods, a problem arises due to the
large size of the treating apparatus. In an apparatus provided with plural
chemicals, treating vessels and rinsing vessels, the occupied area of the
apparatus has to become large. In order to cope with this problem, it is
effective to use an apparatus of the one-bath type wherein pure water and
a plurality of solutions of chemicals are fed to one treating vessel.
An apparatus which has been intended to solve these two problems at the
same time, is a one-bath type Marangoni dryer or a
direct-substitution-with-IPA dryer. The outline of a typical apparatus is
shown in FIG. 14. In FIG. 14, a wafer 2 is immersed in a treating vessel
(treating chamber) 1 wherein the chemicals solution is upflown from a feed
port 3 provided at a lower portion of the treating vessel 1 to etch the
wafer 2. Thereafter, pure water is upflown from the feed port 3 for
rinsing. The chemicals solution and pure water are overflown from the
treating vessel 1 and discharged from a discharge port 4. During the
drying of the wafer 2, IPA vapor is introduced from a feed port 5 into an
upper space 1a of the treating vessel 1, and the wafer 2 is pulled up
therein. This apparatus is of the type wherein the wafer 2 is elevated at
the time of the drying.
FIG. 15 is a schematic view of another type of known wet treating
apparatus. In this apparatus, a chemicals solution is passed for etching
from a feed portion 3 provided at an upper side portion of a treating
vessel 1. Subsequently, pure water is passed from the feed port 3 for
rinsing. The chemicals solution and pure water are discharged from a
discharge port 4 at a lower portion of the treating vessel 1. During the
drying of the wafer 2, the level of the pure water in the treating vessel
1 is lowered and, at the same time, IPA vapor is introduced into an upper
space of the treating vessel 1, followed by movement of the wafer 2 toward
the IPA atmosphere. This apparatus is of the type wherein the water level
is dropped at the time of the drying.
It has been found that where a silicon oxide film (SiO.sub.2) is etched
with hydrofluoric acid (HF) by use of these apparatus, the silicon
substrate is deposited with a multitude of silicon particles on the
surfaces thereof.
Suppose a Si wafer and a silicon oxide film are simultaneously immersed in
a PVC vessel. When the oxide film is etched with HF to a depth of 200
.ANG. and rinsed with water, and then subjected to the Marangoni drying,
several thousands of particles are deposited on the Si wafer.
The formation mechanism of the particles are considered as follows.
Where the silicon oxide is etched with hydrofluoric acid, the following
reaction (1) proceeds to the right side
SiO.sub.2 +6HF=H.sub.2 SiO.sub.6 +2H.sub.2 O (1)
When HF is present, the reaction proceeds to the right side. In a rinsing
sequence, however, the reaction (1) proceeds to the left side. According
to this reverse reaction, SiO.sub.2 is generated. The SiO.sub.2 is present
as Si(OH).sub.4 colloids within the treating vessel, on the wall surfaces
of the vessel, and on the surfaces of the wafer.
It has been found that during the "Marangoni drying" method or the
"direct-substitution-with-IPA drying" method, IPA which is in the vicinity
of the surfaces of the treating vessel in the drying sequence is dissolved
and reacts with colloidal Si(OH).sub.4 thereby forming particles. Because
of the formation of the particles, the one-bath type "Marangoni dryer" or
the "direct-substitution-with-IPA type dryer" has placed limitations on
applications thereof.
As stated hereinabove, with the known one-bath type apparatus of the wet
treatment of semiconductor wafers, semiconductive particles are inevitably
deposited on the semiconductor wafer after drying, thereby presenting a
problem in subsequent semiconductor treating processes. If no particles
are deposited, this method can be applied to the rinsing step of all the
semiconductor wafer treating processes.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a wet treating method
and apparatus which can solve the prior art problems, wherein little or no
semiconductive particles are deposited on a semiconductor wafer after
drying, or at least the deposition is significantly reduced, in the wet
treatment, particularly in a rinsing process, of a semiconductor wafer
using a single treating vessel.
According to one aspect of the present invention, in method for wet
treatment of a semiconductor wafer, a semiconductor wafer is treated in a
treating vessel with a chemicals solution, rinsed with pure water, and
dried by direct transfer to an atmosphere of a vapor containing an
alcohol, wherein the semiconductor wafer is treated with a solution
containing a semiconductive particle-removing agent during the interval
between the treatment with the chemicals solution and the drying.
In this method, the semiconductive particle-removing agent is preferably a
semiconductive particle abherent for preventing adhesion of particles by
controlling the zeta potential of the particles. The semiconductive
particle abherent is preferably selected from either an alcohol,
electrolytically ionized water or a surface active agent.
Alternatively, the semiconductive particle abherent comprises a
semiconductive colloid coagulant capable of coagulating semiconductive
colloids. The semiconductive colloid coagulant is comprised preferably of
aluminium sulfate or polyaluminium chloride.
In another aspect of the present invention, in a method for the wet
treatment of a semiconductor wafer, the semiconductive particle-removing
agent is added to pure water for rinsing, for at least a part of the
rinsing process.
According to another aspect of the present invention, in a method for the
wet treatment of a semiconductor wafer, the semiconductor wafer is treated
with a semiconductive particle-removing agent during the interval between
the treatment with the chemicals solution and the drying.
According to another aspect of the present invention, an apparatus for wet
treatment of a semiconductor wafer is comprised of a wet treating vessel
for wet treating a semiconductor wafer. A means is provided for rinsing
the semiconductor wafer after treatment of the semiconductor wafer with a
chemicals solution in the wet treating vessel. A means is provided for
drying the rinsed semiconductor wafer by direct transfer to an atmosphere
of a vapor containing an alcohol. Further, a means is provided for
treating the semiconductor wafer with a solution containing a
semiconductive particle-removing agent during the interval between the
chemicals treatment and the drying.
According to another aspect of the present invention, an apparatus for wet
treatment of a semiconductor wafer comprises a means for immersing the
semiconductor wafer in a semiconductive particle-removing agent during the
interval between the chemicals treatment and the drying.
In another aspect on the present invention, the apparatus for the wet
treatment of a semiconductor wafer further comprises a means for
collecting the semiconductive particle-removing agent which is discharged
from the wet treating vessel, for future use.
Other features and advantages of the present invention will become more
apparent from the following description taken together with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view showing an arrangement of an apparatus for the
wet treatment of a semiconductor wafer according to the first embodiment
of the present invention.
FIG. 2 is a schematic view showing another type of wet treating apparatus
of the first embodiment of the present invention.
FIG. 3 shows a process of etching a silicon oxide film in the first
embodiment of the present invention.
FIG. 4 is a graph showing the relation between the zeta potential and the
IPA concentration, in a solution for different types of particles of
silicon (Si), silicon oxide film (SiO.sub.2) and polystyrene latex.
FIG. 5 is a graph showing the relation between the zeta potential and the
pH of the solution for different types of semiconductive particles such as
silicon (Si), silicon oxide film (SiO.sub.2) and polystyrene latex.
FIG. 6 is a flowchart showing a process of etching a silicon oxide film in
accordance with the fifth embodiment of the present invention.
FIG. 7 is a flowchart showing a process of etching a silicon oxide film in
accordance with the sixth embodiment of the present invention.
FIG. 8 is a flowchart showing a process of etching a silicon oxide film in
accordance with the seventh embodiment of the present invention.
FIG. 9 is a flowchart showing a process of etching a silicon oxide film in
accordance with the eighth embodiment of the present invention.
FIG. 10 is a flowchart showing a process of etching a silicon oxide film in
accordance with the ninth embodiment of the present invention.
FIG. 11 is a schematic view showing an arrangement of a wet treating
apparatus of the tenth embodiment of the present invention.
FIG. 12 is a schematic view showing another arrangement of the wet treating
apparatus according to the tenth embodiment of the present invention.
FIG. 13 is a schematic view showing an arrangement of a wet treating
apparatus according to the eleventh embodiment of the present invention.
FIG. 14 shows an outline of a typical conventional wet treatment apparatus.
FIG. 15 is a schematic view of another type of conventional wet treating
apparatus.
BEST MODE OF CARRYING OUT THE INVENTION
This invention will be described in further detail by way of example with
reference to the accompanying drawings.
First Embodiment
FIG. 1 is a schematic view showing an arrangement of an apparatus for the
wet treatment of a semiconductor wafer according to the first embodiment
of the present invention. In FIG. 1, indicated by 1 is a treating vessel
(treating chamber); indicated by 1a is the upper space of the treating
vessel 1; indicated by 2 is a wafer to be treated; indicated by 3 is a
pipe for feeding a chemicals solution and pure water to the treating
vessel 1; indicated by 4 is a discharge pipe for discharging the chemicals
solution and pure water from the treating vessel after the treatment; and
indicated by 5 is a pipe provided at the upper space 1a of the treating
vessel 1 to feed IPA vapor necessary for the drying of the wafer 2.
Reference numeral 6 indicates an introduction port for introducing a
particle-removing agent, or a solution containing a particle-removing
agent, from the bottom of the treating vessel.
This wet treating apparatus is of the type wherein the chemicals solution
and pure water are, respectively, fed from the feed port 3 at the bottom
of the treating vessel 1, and the chemicals solution and the like after
the treatment are overflown from the upper portion of the treating vessel
1. Further, the apparatus is of the type wherein the wafer 2 is pulled up
from the pure water and the like in the treating vessel.
FIG. 2 is a schematic view showing another type of wet treating apparatus
of the first embodiment of the invention. This apparatus is of the type
wherein the chemicals solution and pure water are, respectively, fed from
the feed port 3, and the chemicals solution and the like after the
treatment is discharged from the discharge port 4 provided at the bottom
of the treating vessel 1. An additive for particle removal or a solution
containing a particle-removing agent is introduced from the introduction
port 6 at the upper portion of the vessel 1. After the treatment of the
wafer 2, the level of pure water and the like is lowered and the wafer is
removed.
In this first embodiment, the chemicals solution of hydrofluoric acid used
for etching a silicon oxide film, should usually have an impurity metal
concentration of 1 ppm or below, and should contain 100/cc or below of
fine particles with a size of 0.2 .mu.m or below. The pure water for
rinsing should have a value of 18 M.OMEGA. or above and contain 5/cc or
below of fine particles with a size of 0.05 .mu.m and above.
FIG. 3 shows a process of etching a silicon oxide film in this embodiment.
As is particularly shown in the sequence of FIG. 3, the film was etched
with 0.25 wt % hydrofluoric acid (HF) for 300 seconds, and rinsed with 22
liters/minute of water for 15 minutes. After stopping the feed of the pure
water, 300 cc of isopropyl alcohol (IPA, this alcohol may be sometimes
referred to as IPA hereinafter) was added as a particle-removing agent, to
the treating vessel 1 in which about 20 liters of the pure water was left,
following which the wafer was allowed to stand for 5 minutes.
Subsequently, the wafer was pulled up at a rate of 5 mm/second in an IPA
atmosphere, and particles having a size of 0.17 .mu.m or above were
deposited on the wafer, and were found to be 50 or below in number.
FIG. 4 is a graph showing the relation between the zeta potential and the
IPA concentration in the solution for different types of particles of
silicon (Si), silicon oxide film (SiO.sub.2) and polystyrene latex. As
shown in FIG. 4, as the IPA concentration increases, the absolute value of
the zeta potential of the respective types of particles decreases. The
zeta potential is a potential on a solid surface in a liquid. The decrease
in absolute value of the zeta potential indicates an adhesion force which
becomes smaller.
In the above treatment, the particles are formed in the treating vessel 1.
Due to the presence of the forcedly added IPA, the absolute value of the
zeta potential decreases as shown in FIG. 4, and the particles are
unlikely to deposit. Thus, the number of particles deposited on the wafer
can be significantly reduced.
Thus, in a process or apparatus of the type wherein, after chemicals
treatment in one treating vessel and subsequent rinsing, a semiconductor
wafer immersed in very pure water is dried by direct substitution of the
water on the surfaces thereof, with a vapor containing an alcohol, a
sequence of adding, an alcohol or a solution containing an alcohol, to the
treating vessel is provided between the steps of the chemicals treatment
and the drying. Because the added alcohol, IPA for example, is very
effective, the particles deposited on the wafer after drying can be
reduced largely in number.
The process of adding an alcohol set out in this embodiment has been
illustrated as an addition to pure water left or remaining after rinsing.
Other addition procedures may be used as will be described hereinafter.
Second Embodiment
In a second embodiment of the present invention, a wet treating apparatus
shown in FIG. 1 or 2 is used. A hydrofluoric acid solution used to etch a
silicon oxide film and pure water for rinsing are those which,
respectively, have similar characteristics as illustrated in the first
embodiment.
The process of etching a silicon oxide film is similar to that set out with
reference to FIG. 3 in connection with the first embodiment, except that
in the second embodiment, electrolytically ionized water is used as an
additive for removal of the semiconductive particles. In a specific
treating instance, where OH-ionized water produced by electrolytic
decomposition was added as an electrolytically ionized water, and the
wafer was pulled up in an IPA atmosphere, particles having a size of 0.17
m or above and deposited on the wafer were found to be 50 or below in
number.
FIG. 5 is a graph showing the relation between the zeta potential and the
pH of the solution for different types of semiconductive particles such as
silicon (Si), silicon oxide film (SiO.sub.2) and polystyrene latex. If the
solution has a certain level of pH, the zeta potentials of these particles
and the Si substrate become the same with respect to the polarity thereof,
and the values thereof come close to each other.
In the above treatment, the particles are formed in the treating vessel 1.
Since the forcedly added, electrolytically ionized water is alkaline in
nature, and the polarities of the zeta potentials become the same as shown
in FIG. 5 due to the presence of electrolytically ionized water, the
particles are unlikely to deposit. Thus, the particles deposited on the
wafer are significantly reduced in number.
Thus, in a process or apparatus of the type wherein, after chemicals
treatment in one treating vessel and subsequent rinsing, a semiconductor
wafer immersed in very pure water is dried by direct substitution of the
water on the surfaces thereof with a vapor containing an alcohol, a
sequence of adding electrolytically ionized water to the treating vessel
is provided between the steps of the chemicals treatment and the drying.
Because the electrolytically ionized water is very effective, OH-ionized
water for example, the particles deposited on the wafer after drying can
be significantly reduced in number.
The process of adding electrolytically ionized water set out in this
embodiment has been illustrated as an addition to pure water remaining
after rinsing. Other addition procedures may be used as will be described
hereinafter.
Third Embodiment
In the third embodiment of the present invention, a wet treating apparatus
is of the type shown in FIG. 1 or 2. A hydrofluoric acid solution used to
etch a silicon oxide film and pure water for rinsing are those which,
respectively, have similar characteristics as illustrated in the first
embodiment.
The process of etching a silicon oxide film is similar to that set out with
reference to FIG. 3 in the first embodiment, except that in the third
embodiment 3, a surface active agent is used as an additive for removal of
semiconductive particles.
In a specific treating instance, after stopping of the feed of pure water
for rinsing, an anionic surface active agent was added in an amount of 1
ppm, and the wafer was allowed to stand for 5 minutes. Thereafter, the
wafer was pulled up in an IPA atmosphere, whereupon it was found that
particles having a size of 0.17 .mu.m or above and deposited on the wafer,
were 50 or below in number.
In the above treatment, the particles are formed in he treating vessel. The
zeta potential polarity is reversed, owing to the forcedly added surface
active agent, and becomes the same as the polarity of the potential of the
Si substrate, with the unlikelihood that the particles are deposited on
the wafer.
Thus, in a process or apparatus of the type wherein, after chemicals
treatment in one treating vessel and subsequent rinsing, a semiconductor
wafer immersed in very pure water is dried by direct substitution of the
water on the surface thereof, with a vapor containing an alcohol. A
sequence of adding a surface active agent or a solution containing a
surface active agent to the treating vessel is provided between the steps
of the chemicals treatment and the drying. Because the surface active
agent added, an anionic or cationic surface active agent, for example, is
very effective, the particles deposited on the wafer after drying can be
significantly reduced in number.
The process of adding the surface active agent set out in this embodiment
has been illustrated as an addition to pure water remaining after rinsing.
Other addition procedures may be used as will be described hereinafter.
Fourth Embodiment
In the fourth embodiment of the present invention, a wet treating apparatus
is of the type shown in FIG. 1 or 2. A hydrofluoric acid solution used to
etch a silicon oxide film and pure water for rinsing are those which,
respectively, have similar characteristics as illustrated in the first
embodiment.
The process of etching a silicon oxide film is similar to that set out with
reference to FIG. 3 in the first embodiment except that in the fourth
embodiment, a coagulant capable of coagulating colloidal Si(OH).sub.4 is
used as an additive for removal of semiconductive particles. Coagulants
such as aluminum sulfate, electrolytic aluminum, polyaluminum chloride and
the like have the function of coagulating colloidal Si(OH).sub.4. Thus, a
source of forming particles can be removed. In the above treatment, the
particles are formed in the treating vessel 1. However, the forcedly added
coagulants, such as aluminum sulfate, electrolytic aluminum, polyaluminum
chloride and the like, have the function of coagulating colloidal
Si(OH).sub.4. Thus, a source of forming particles can be removed.
Thus, in a process or apparatus of the type wherein, after chemicals
treatment in one treating vessel and subsequent rinsing, a semiconductor
wafer immersed in very pure water is dried by direct substitution of the
water on the surfaces thereof, with a vapor containing an alcohol. A
sequence of adding a coagulant or a solution containing a coagulant to the
treating vessel is provided between the steps of the chemicals treatment
and the drying. Aluminum sulfate, electrolytic aluminum, and polyaluminum
chloride are very effective as the coagulant. Thus, the particles
deposited on the wafer after drying can be significantly reduced in
number.
The process of adding the coagulant set out in this embodiment has been
illustrated as addition to pure water stayed after rinsing. Other addition
procedures may be used as will be described hereinafter.
Fifth Embodiment
In the fifth embodiment of the present invention, a wet treating apparatus
is of the type shown in FIG. 1 or 2. A hydrofluoric acid solution used to
etch a silicon oxide film and pure water for rinsing, are those which have
respectively been illustrated in the first embodiment. A particle-
removing agent may be any of those described in the first to fourth
embodiments.
FIG. 6 is a flowchart showing a process of etching a silicon oxide film in
accordance with this embodiment.
In a specific example, as shown in a flow chart of FIG. 6, 0.25 wt % of HF
is used for etching treatment for 300 seconds, followed by rinsing with 22
liters/minute of water for 15 minutes. After the rinsing, pure water
containing a semiconductive particle-removing agent is fed for further
rinsing.
The added semiconductive particle-removing agent may be any of the
following: alcohol, electrolytically ionized water, surface active agents,
and/or coagulants as illustrated in the first to fourth embodiments.
When alcohols, electrolytically ionized water and surface active agents are
used as a particle-removing agent, the zeta potential of semiconductive
colloids can be changed, so that the removal of absorbed colloids is
promoted, thereby eliminating a source for particles. The rinsing with the
pure water, to which a particle-removing agent has been added, permits
colloidal Si(OH).sub.4 serving as a particle source, to be completely
removed and discharged at the time of the rinsing.
Aluminum sulfate, electrolytic aluminum or polyaluminum chloride, which is
used as a coagulant additive, is effective for coagulating colloidal
Si(OH).sub.4, thereby removing a source for particles. When pure water to
which a coagulant for the particles has been added is fed for rinsing,
colloidal Si(OH).sub.4, which is a particle source, is coagulated and can
be completely removed at the time of rinsing.
As stated above, according to this embodiment, a wafer is treated with a
chemical solution and rinsed with water, followed by further rinsing with
pure water, to which a particle-removing agent has been added. In doing
so, the particle source is discharged along with rinsing water, thereby
preventing the particles from deposition on the wafer.
Sixth Embodiment
In the sixth embodiment of the present invention, a wet treating apparatus
is of the type shown in FIG. 1 or 2. A hydrofluoric acid solution, used to
etch a silicon oxide film, and pure water for rinsing are those which
have, respectively, been illustrated in the first embodiment.
FIG. 7 is a flowchart showing a process of etching a silicon oxide film in
accordance with this embodiment.
In a specific example, as shown in a sequence of FIG. 7, 0.25 wt % of HF is
used for etching treatment for 300 seconds, followed by feeding pure water
for rinsing at a rate of 22 liters/minute for 15 minutes, while adding a
semiconductive particle-removing agent. Thereafter, the wafer was pulled
up in an IPA atmosphere.
The added semiconductive particle-removing agent may be any of the
following: alcohol, electrolytically ionized water, surface active agents,
and/or coagulants, as illustrated in the first to fourth embodiments.
When alcohol, electrolytically ionized water or surface active agents are
used as a particle-removing agent, the zeta potential of colloids can be
changed so that the removal of absorbed colloids is promoted, thereby
eliminating a source for the particles. Thus, the colloidal Si(OH).sub.4
which is a source for the particles, can be completely removed at the time
of the rinsing.
If an alcohol is added, the concentration of the alcohol may range from the
order of magnitude of ppm to 100 wt %. At the time of the rinsing, the
invariable addition may be continued.
Where electrolytically ionized water is used, rinsing may be effected using
only electrolytically ionized water.
With a surface active agent, the rinsing may be effected while invariably
adding the agent.
Using these rinsing procedures, one can obtain not only the effect of
suppressing the deposition of the particles, but also the effects of
promoting the removal of adsorbed colloids and also the effects of
promoting the discharge of the colloids to the outside by means of the
running water.
The coagulant such as aluminum sulfate, electrolytic aluminim, polyaluminim
chloride or the like which is used as an additive is capable of
coagulating colloidal Si(OH).sub.4 and can remove a source for producing
particles.
As stated above, in this embodiment, the rinsing is effected, after the
chemicals treatment of the wafer, by use of pure water to which a
particle-removing agent has been added from the beginning. In doing so,
the particle source can be discharged along with the rinsing water thereby
preventing the deposition of particles on the wafer.
Seventh Embodiment
In the seventh embodiment of the invention, a wet treating apparatus is of
the type shown in FIG. 1 or 2. A hydrofluoric acid solution used to etch a
silicon oxide film and pure water for rinsing are those which,
respectively, have those characteristics as illustrated in the first
embodiment.
FIG. 8 is a flowchart showing a process of etching a silicon oxide film in
accordance with the seventh embodiment.
In a specific example, as shown in a sequence of FIG. 8, 0.25 wt % of HF is
used for etching treatment for 300 seconds, followed by feeding pure water
for rinsing at a rate of 22 liters/minute for 15 minutes, while
introducing an additive for removal of particles and then rinsing with
pure water alone.
The introduced additive may be any of the following: alcohol,
electrolytically ionized water, surface active agents, and/or coagulants
illustrated in the first to fourth embodiments. The functions and effects
of these additives are as illustrated in the sixth embodiment and are not
repeated herein.
This embodiment is advantageous in that where a coagulant or a surface
active agent is added under the apprehension that such a particle-removing
agent is left on the wafer surface, a sequence of rinsing with pure water
alone is involved after rinsing with pure water containing the
particle-removing agent, and the removing agent is thereby prevented from
being deposited on the wafer.
Eighth Embodiment
In the eighth embodiment of the present invention, a wet treating apparatus
is of the type shown in FIG. 1 or 2. A hydrofluoric acid solution used to
etch a silicon oxide film and pure water for rinsing are ones which,
respectively, have those characteristics as illustrated in the first
embodiment.
FIG. 9 is a flowchart showing a process of etching a silicon oxide film in
accordance with the eighth embodiment.
In a specific example, as shown in a sequence of FIG. 9, 0.25 wt % of HF is
used for etching treatment for 300 seconds, followed by substituting the
HF aqueous solution with a particle-removing agent and then rinsing with
pure water. The resultant wafer is pulled up in an IPA atmosphere. In this
case, the substitution with the particle-removing agent would include a
case where a particle-removing agent is run for the treatment, and a case
where a semiconductor wafer is immersed in a dead particle-removing agent.
[0049]
The particle-removing agent used for the substitution may be any of the
following: alcohol, electrolytically ionized water, surface active agents,
and/or coagulants illustrated in the first to fourth embodiments.
When alcohol, electrolytically ionized water or surface active agents are
used as a particle-removing agent, the zeta potential of colloids can be
changed, so that the removal of absorbed colloids is promoted, thereby
eliminating a source for the particles. Thus, the colloidal Si(OH).sub.4
which is a source for the particles can be completely removed at the time
of the rinsing.
Using these rinsing procedures, one can obtain not only the effect of
suppressing the deposition of the particles, but also the effects of
promoting the removal of adsorbed colloids and also the effects of
promoting the discharge of the colloids to the outside by means of the
running water.
When the coagulant such as aluminum sulfate, electrolytic aluminum,
polyaluminum chloride or the like is used as an additive, colloidal
Si(OH).sub.4 can be coagulated thereby removing a source for producing
particles. The colloidal Si(OH).sub.4 which is a source for particles, can
be completely discharged to the outside at the time of rinsing.
As stated above, in this embodiment, the chemicals solution is substituted
with a particle-removing agent, such as an alcohol or electrolytically
ionized water, after the chemicals treatment of the wafer. Thereafter, the
wafer is rinsed with pure water, followed by placement in an atmosphere of
an alcohol vapor. In doing so, the deposition of the particles on the
wafer can be prevented.
Ninth Embodiment
In the ninth embodiment of the present invention, a wet treating apparatus
is of the type shown in FIG. 1 or 2. A hydrofluoric acid solution used to
etch a silicon oxide film and pure water for rinsing are those which,
respectively, have those characteristics as illustrated in the first
embodiment.
FIG. 10 is a flowchart showing a process of etching a silicon oxide film in
accordance with the ninth embodiment. In a specific example, as shown in a
sequence of FIG. 10, 0.25 wt % of HF is used for etching treatment for 300
seconds, followed by rinsing with pure water and substituting the pure
water with a particle-removing agent. Thereafter, the wafer is pulled up
in an IPA atmosphere.
The particle-removing agent used for the substitution may be any of the
following: alcohol, electrolytically ionized water, surface active agents,
and/or coagulants illustrated in the first to fourth embodiments. The
functions and effects of these additives are as illustrated in the eighth
embodiment and are not repeated herein.
As stated above, in this embodiment, the pure water in the treating vessel
is substituted with a particle-removing agent such as an alcohol or
electrolytically ionized water, followed by drying. The substitution with
a particle-removing agent includes cases where a particle-removing agent
is run or where the semiconductor wafer is immersed in a dead
particle-removing agent.
In this way, the deposition of the particles on the wafer can be prevented.
Tenth Embodiment
FIG. 11 is a schematic view showing an arrangement of a wet treating
apparatus of the tenth embodiment of the present invention. In FIG. 11,
reference numeral 6a indicates sprays provided at a ceiling of the
treating vessel 11, from which a particle-removing agent in the form of a
liquid phase is sprayed. In this apparatus, a feed portion for chemicals
is removed from the apparatus of FIG. 1. Instead, the spray 6a is
provided. Other structure is similar to that of FIG. 1 and is not set out
herein.
FIG. 12 is a schematic view showing another arrangement of the wet treating
device according to the tenth embodiment of the present invention. In
place of the feed port 6 for chemicals in the apparatus of FIG. 2, a spray
6a for chemicals solution is attached to the ceiling of the treating
vessel 1. Other structure is similar to that of FIG. 2 and is not
explained herein.
In the tenth embodiment, a hydrofluoric acid solution used to etch a
silicon oxide film and pure water for rinsing have respectively those
characteristics as illustrated in the first embodiment.
The particle-removing agent used in this embodiment may be any of the
following: alcohol, electrolytically ionized water, surface active agents,
and/or coagulants illustrated in the first to fourth embodiments.
The manner of addition of the semiconductor particle-removing agent
includes spraying a liquid phase of the agent from the ceiling of the
treating vessel 1 toward pure water for rinsing. Much of the
semiconductive particles are formed in the vicinity of the water surface
by reaction between the IPA dissolved, from the IPA atmosphere, in the
water in the treating vessel and the colloidal Si(OH).sub.4 in the
treating vessel. Accordingly, when the particle-removing agent is
predominantly added to the vicinity of the water surface, the particles
can be efficiently removed, resulting in the reduction in amount of the
agent.
In the first to seventh embodiments, the process of etching a silicon oxide
film, includes adding a particle-removing agent from the introduction port
6 to pure water, or substituting the agent with pure water. In contrast,
according to this embodiment, a liquid phase agent is sprayed from the
ceiling of the treating vessel as set out above. Otherwise, the wafer
treating process is similar to that of the first to seventh embodiments
and is not repeatedly explained.
In this way, according to this embodiment, the particle-removing agent is
supplied predominantly at the boundary between the water and the IPA
vapor, thereby causing the particles to be removed efficiently.
Eleventh Embodiment
FIG. 13 is a schematic view showing an arrangement of a wet treating
apparatus according to the eleventh embodiment of the present invention.
In FIG. 13, reference numeral 7 indicates a collecting and purifying means
for particle-removing agents such as alcohol. Reference numeral 8
indicates a tank for temporarily storing a collected and purified
particle-removing agent such as an alcohol, and reference numeral 9
indicates a port for charging a fresh particle-removing agent.
The treatment of a wafer in a treating vessel 1 is carried out in a manner
similar to that illustrated in the first to tenth embodiments. In this
embodiment, a particle-removing agent is collected from waste water
discharged from a discharge port 4 of the vessel 1, and purified by
collecting and purifying means 7, followed by storage in a tank 8. The
stored particle-removing agent is re-used by introduction from an
introduction port 6 into the vessel 1, along with a fresh
particle-removing agent charged from a port 9. Thus, the particle-removing
agent such as an alcohol can be effectively used.
The wafer treating process, and the type, function and effect of the
particle-removing agent are similar to those of the first to tenth
embodiments and are not explained repeatedly.
As described above, the present invention has the following effects and
advantages.
According to the present invention, there is provided a process for the wet
treatment of a semiconductor wafer, which is comprised of subjecting a
semiconductor wafer to chemicals treatment, rinsing with pure water, and
drying by direct transfer to an atmosphere of a vapor containing an
alcohol, wherein the semiconductor wafer is treated with a solution
containing a semiconductive particle-removing agent during the interval
between the steps of the chemicals treatment and the drying, whereby the
particles can be prevented from being deposited on the wafer, and can be
reduced significantly in number.
Further, according to the present invention, the semiconductor wafer may be
immersed in a semiconductive particle-removing agent during the interval
between the steps of the chemicals treatment and the drying, whereby the
particles can be prevented from being deposited on the wafer and can be
reduced significantly in number.
Additionally, according to the present invention, a wet treating apparatus
for treating a semiconductor wafer is obtained on the basis of the above
wet treating method, with which the deposition of the particles on the
semiconductor wafer can be prevented or reduced.
Obviously, numerous additional modifications and variations of the present
invention are possible in light of the above teachings. It is therefore to
be understood that within the scope of the appended claims, the present
invention may be practiced otherwise than as specifically described
herein.
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